Small Molecule Control of Virulence Gene Expression in Francisella tularensis
Figure 8
PigR interacts with the MglA-SspA complex.
(A) Schematic representation of the bacterial bridge-hybrid system used to detect an interaction between PigR and the MglA-SspA complex. In this system F. tularensis SspA interacts with the MglA-ω fusion protein to form a heteromeric complex that associates with E. coli RNAP. Contact between the heteromeric MglA-SspA complex displayed on RNAP and the DNA-bound PigR-Zif fusion activates transcription from the test promoter driving expression of lacZ. The test promoter placZif1-61 is present on an F′ episome in E. coli strain KDZif1ΔZ and bears a Zif binding site centered 61 bp upstream of the transcription start site of the lac core promoter (whose −10 and −35 elements are indicated). (B) Transcription activation by PigR-Zif in the presence of F. tularensis SspA and the MglA-ω fusion protein. Assays were performed with cells of the E. coli reporter strain KDZif1ΔZ containing compatible plasmids that directed the IPTG-controlled synthesis of the indicated proteins. Cells were grown in the presence of different concentrations of IPTG and assayed for β-galactosidase activity.